Heliograph

From George Eastman House : Notes On Photographs

Heliography, sun writing, is the name given to the asphalt
system of imaging invented by Joseph-Nicéphore Niépce in
1822. Interested in the new lithographic printing process,
Niépce was seeking a simplifi ed way to print multiple impressions
from a single master. He knew that bitumen of Judea
asphaltum used as a resist in engraving, hardened after exposure
to light. He coated a variety of materials and contact
printed engravings on paper that he had oiled to enhance
its translucency. After washing in several different solvents,
the asphalt that was in contact with the inked lines of the
engraving was washed away exposing the support below.

Niépce used glass, zinc, copper, lithographic stone, pewter,
and silver-surfaced copper plates. In 1826, he succeeded
in making what is now generally accepted to be the first
permanent, camera-made image. He took one of his plates
and placed it in a camera that he pointed out a second story
window of his estate, Le Gras, near Chalon-sur-Saône in
central France. The plate required at least one day exposure to
record an image. After removing the unexposed areas of the
asphaltum with a solvent, a direct positive image was visible
against the polished background of the plate.[1]